Angular contact, double row ball bearings have a pair of inner and outer, coaxial races, each of which has a pair of ball pathways. The two ball pathways on one race face axially outwardly, and are closer together axially, while the two ball pathways on the opposite race face axially inwardly, and are spaced father apart axially. Each pathway on each race is diagonally opposed to a pathway on the opposite race, with a row of balls engaged between each opposed pathway pair. The clearance between the opposed pathway pairs, which has a radial and axial component, must be less than a ball diameter. By diagonally opposed, it is meant that the opposed pathway pair engages opposed quadrants on the balls in its row, and the ball contact areas (narrow annuli) on the opposed pathways lie on a cone. This can easily be seen in the coassigned patent to Lura et al., U.S. Pat. No. 4,179,167. Referring to FIG. 1, the closer, axially outwardly facing pathways 38 and 40 lie on the outer race (hub) 34, while the axially inwardly facing pathways 22 and 48 are on the inner race (spindle) 14. In such a configuration, the two contact cones, shown by dotted lines, converge and intersect at a medial plane located between the ball rows 44 and 46. The other possible angular contact configuration would have the axially outwardly facing pathways on the inner race, in which case the contact cones would diverge. That configuration is not very common or practical in most bearing applications.
In any angular contact bearing, convergent or divergent, one ball row is installed last. The last installed ball row can be installed by the so called Conrad technique, in which one race is pulled eccentric with respect to the other, creating a crescent shaped space between them that is larger than the ball diameter over a limited angle. Balls may be inserted at the larger, wider part of the crescent in a bunched up pattern, then spaced out evenly and caged after the races are returned to a concentric orientation with the original, smaller pathway clearance. However, a full complement of balls cannot be installed this way, so load capacity is often unacceptable. To install a full complement of balls in the last installed row, a separate race piece is provided that incorporates one of the ball pathways. This is done in Lura, where the separate race piece 50 incorporates the outermost, axially inwardly facing pathway 48 of the last installed ball row 46. It is a relatively simple matter to install the separate race piece when it incorporates an axially inwardly facing pathway, as it may simply be pushed axially in after the last ball row 46 is installed, and then fixed in place. The separate race piece 48 makes solid, continuous contact with the hub 14, so the contact cone of the ball row 46 intersects solid, load supporting metal at all critical points.
It is also known, in an angular contact bearing, to instead incorporate an axially outwardly facing ball pathway in the separable race piece, rather than the axially inwardly facing pathway. This is a more difficult technique, since the outwardly facing ball pathway is axially inboard of, not outboard of, the last installed ball row. Therefore, the separable race piece has to be first pushed axially into the race to which it will ultimately be fixed, after which the last ball row is installed. Finally, the separable race piece is pulled axially back out against the last ball row. The separate race piece is then fixed in place. Thus, the axially outwardly facing pathway can, in effect, be installed "behind" and inside of the last installed ball row.
A known bearing design that incorporates an axially outwardly facing ball pathway as part of a separate piece is shown in U.S. Pat. No. 4,569,602 to Lundgren. Structural compromises are made to allow assembly in that fashion, however, which make the design unacceptable in terms of load support, and which also make for a non compact design, characteristics either of which would make the basic design impossible to use as a vehicle wheel bearing or any other substantial load bearing application. An embodiment from the Lundgren patent is reproduced in FIG. 5 to illustrate.
Referring to FIG. 5, a basic, two row angular contact bearing includes a ball row 21" which is installed last, and which is engaged between an axially inwardly facing pathway 18" on inner race 11" and an axially outwardly facing pathway 29", which is incorporated in a separate race piece 27". The contact cone for the ball row 21" is shown at C, and the pitch plane, which is a plane through the pitch circle of ball row 21" and perpendicular to the central axis, is indicated at P. In addition, an imaginary cylindrical surface which establishes the radially outermost extent of the ball row 21" is indicated at O.sub.R, and a plane which establishes its axially outermost extent is indicated at O.sub.A. The cylindrical inner surface 46 of the outer race 25" extends axially out substantially beyond the pitch plane P to an edge 48, and it is substantially radially spaced from O.sub.R, by almost a full diameter of a ball 21". The cylindrical outer surface 50 of separate race piece 27" extends axially from a point substantially outboard of pitch plane P to a point just barely inboard of edge 48, with a gap 30" therebetween. Although not illustrated, gap 30" would be filled with a ring or the like to keep ball row 21" firmly engaged between the pathways 18" and 29". Gap 30" is large enough to in turn allow separate race piece 27" to be pushed axially into outer race 25" far enough to create enough clearance between the pathways 18" and race piece 27" to allow the ball row 21" to be installed between them. However, because edge 48 is located so far axially outboard, flange 52 has to be located even farther outboard of the plane O.sub.A in order to allow a large enough gap 30". This lack of compactness in the axial direction is compounded. Because flange 52 is located so far axially outboard, surface 50 in turn has to be located substantially radially outboard of O.sub.R. Otherwise, shifting flange 52 axially in would still not allow enough total axial and radial clearance between the pathways 18" and 29" for the ball row 21" to clear. Worse than the lack of compactness is the fact that there is very little axial overlap, indicated at X, between the outer race surface 46 and the separate race piece surface 50. What overlap there is lies outboard of the pitch plane P, so that the contact cone C passes through no solidly contacting bearing material at all. As a consequence, the bearing is essentially useless for any load bearing application, such as a vehicle wheel bearing.
It is, therefore, a general object of the invention to provide an angular contact bearing which can be assembled by placing the axially outwardly facing pathway for the last installed ball row on a separate, slidable race piece, but with enough strategically placed solid contact between the outer race and the separate race piece to allow for good load support.
It is another object of the invention to provide such a bearing that is axially and radially compact.